Mendel Stabilization

Okay - I am a nubie here - sorry.

My plan (prior to world domination anyway) is to buy a Mendel Kit to get PLAcclimated to 3D printing in the real world, then use it to print the parts for a Delta of my own design (for speed,accuracy and build volume) then use the Delta for rapid prototyping and short run production of parts in my own company and maybe someday for others. While being new to 3D printing I do have some CNC expertise, so some of the technology is the same, I just need to learn to think in additive instead of subtractive mode.

Having ordered a cheap Chinese Mendel Kit and having some days to ponder while it makes it's way to this continent, I have collected a couple questions and thought I would start fishing for answers early.

My being ridiculously frugal led me to consider the Mendel and Prusa styles for my first foray into the realm of 3D printing, and I finally landed on a Mendel. In looking at the mechanics of the Mendel, it seemed better stabilized in one axis (that is the front and back motion of the table) as compared to the Prusa, but there does not seem to be any stabilization along the other Axis (combating the back and forth of the print head itself). I imagine the square frame of the Prusa was meant to provide that stabilization.

My first question, one of many to be sure, is: Has anyone added a pair of diagonal legs or outriggers if you will, to the sides of a Mendel? Just an extra pair of threaded rods from the top of the Z axis to a new "Foot" and a longer threaded rod holding the bottoms of the Z axis together and extending out on each side to those feet. Two extra pieces to print in the kit (the feet), and maybe 6 more inches of width in the machine footprint, extra threaded rod and hardware etc., but i would suspect a substantial increase in the stability of the machine. The model I ordered does use a Bowden tube extruder to minimize the moving mass, but especially on direct feed machines with the stepper motor moving I would think it would add tremendously to print quality, especially taller (or is the correct term thicker?) prints.

Thoughts?

I've just tried wobbling my Mendel about and I think the easiest increase in stiffness would be to fix the feet to a solid base and to fix the Z axis smooth rod bottom support threaded rod (outside of the smooth rod clamp) to the same base - should be a trivial task and would make quite a difference in lateral rigidity. In fact I might try it - I haven't really looked at stiffness because the sprung bed is so flexible I didn't think it worth bothering with (I'm also using it to build a (hopefully) better machine) but I have some suitable plywood and it will only take a few minutes to knock up the brackets.

If I manage to excavate enough of the garage to find my panel saw, I'll let you know how it goes :-)

Well, I tried it and it made quite a difference!

Files on Thingiverse - [www.youmagine.com]

I'm guessing it's now twice as stiff laterally. I just tried a test print and there was noticeably less overshoot at the corner - I suspect going further isn't really necessary since the X axis (bed) stiffness is now the limiting factor and if you're just using it to bootstrap your delta you can print the perimeters very slowly to get the accuracy.

Talking of accuracy, a lot of the Mendel's accuracy comes from how careful you are when building it so get it as close as you can (the smooth rods should be as near as you can get to 90 degrees to each other and dead parallel within an axis) and then print some reasonably large test pieces to check and make final tweaks. A good quality engineers square and spirit level will be useful as will a level surface (if your kitchen fitters were any good, the worktop is often pretty flat and level).

Thanks for the idea :-)

I will mention to the better half that I should build this on the kitchen counter. And if the hospital has WiFi I will let you know how that went.

But I do have machined flat surfaces to build on and a piece of HDO to fasten the printer to.

Thank you for the suggestion.